Solar cell and method of fabrication thereof

Abstract

A solar cell and a method of fabricating solar cells. The method includes a step of separating neighbor solar cells formed on a semiconductor wafer by scribing the wafer to form scribe lines on the wafer and applying a force at, or adjacent to, the scribed lines to separate the solar cells. The scribing is effected on a cap layer covering a window layer of solar cells, thereby minimizing damage to the window layer and mitigating propagation of defects into p-n junctions formed in the solar cells.

1 . A solar cell made of semiconductor materials, the solar cell having a crystalline structure with crystal planes, the solar cell comprising:
 a germanium substrate;   at least one p-n junction formed atop the germanium substrate, the at least one p-n junction including one or more group III elements and one or more group V elements;   a solar cell window layer formed atop the at least one p-n junction;   a patterned cap layer formed atop the solar cell window layer, the patterned cap layer being electrically connected to the solar cell window layer, the patterned cap layer exposing a light-input portion of the solar cell window layer, the patterned cap layer having a cap layer top surface;   a sidewall extending from the top of the patterned cap layer to the bottom of the germanium substrate;   a side piece adjacent the sidewall, the side piece having a side piece top surface, the side piece top surface being substantially level with the patterned cap layer top surface; and   a metal layer formed on a portion of the patterned cap layer and on a portion of the side piece, the metal layer defining a busbar of the solar cell, the busbar bridging the side piece and the patterned cap layer, the metal layer being formed above the at least one p-n junction.   
     
     
         2 . The solar cell of  claim 1  wherein the sidewall has a cleaved surface, the cleaved surface being parallel to a cleaving plane of the solar cell, the cleaved surface not being a sawed surface, the cleaving plane being parallel to a crystal plane of the solar cell. 
     
     
         3 . A solar cell made of semiconductor materials, the solar cell having a crystalline structure with crystal planes, the solar cell comprising:
 a germanium substrate;   at least one p-n junction formed atop the germanium substrate, the at least one p-n junction including one or more group III elements and one or more group V elements;   a solar cell window layer formed atop the at least one p-n junction;   a patterned cap layer formed atop the solar cell window layer, the patterned cap layer being electrically connected to the solar cell window layer, the patterned cap layer exposing a light-input portion of the solar cell window layer, the patterned cap layer having a patterned cap layer top surface;   an electrical insulator layer formed on a portion of the patterned cap layer;   a sidewall extending along a height of the patterned cap layer and towards the germanium substrate;   a side piece adjacent the sidewall, the side piece having a side piece top surface, the side piece top surface being substantially level with the patterned cap layer top surface; and   a metal layer formed on a portion of the electrical insulator layer and on a portion of the side piece, the metal layer defining a busbar of the solar cell, the busbar bridging the side piece and the electrical insulator layer, the metal layer being formed above the at least one p-n junction.   
     
     
         4 . The solar cell of  claim 3  wherein the sidewall has a cleaved surface, the cleaved surface being parallel to a cleaving plane of the solar cell, the cleaved surface not being a sawed surface, the cleaving plane being parallel to a crystal plane of the solar cell. 
     
     
         5 . A solar cell made of semiconductor materials, the solar cell having a crystalline structure with crystal planes, the solar cell comprising:
 a germanium substrate;   at least one p-n junction formed atop the germanium substrate, the at least one p-n junction including group III elements and group V elements;   a solar cell window layer formed atop the at least one p-n junction;   a patterned cap layer formed atop the solar cell window layer, the patterned cap layer being electrically connected to the solar cell window layer, the patterned cap layer exposing a light-input portion of the solar cell window layer, the patterned cap layer having a patterned cap layer top surface;   an electrical insulator layer formed atop the solar cell window layer, adjacent the patterned cap layer;   a sidewall extending along a height of the electrical insulator layer and towards the germanium substrate;   a side piece adjacent the sidewall, the side piece having a side piece top surface, the side piece top surface being substantially level with the patterned cap layer top surface; and   a metal layer formed on a portion of the electrical insulator layer, on a portion of the side piece, and on a portion of the patterned cap layer, the metal layer defining a busbar of the solar cell, the busbar bridging the side piece, the insulator, and the patterned cap layer, the metal layer being formed above the at least one p-n junction.   
     
     
         6 . The solar cell of  claim 5  wherein the sidewall has a cleaved surface, the cleaved surface being parallel to a cleaving plane of the solar cell, the cleaved surface not being a sawed surface, the cleaving plane being parallel to a crystal plane of the solar cell. 
     
     
         7 . A solar cell made of semiconductor materials, the solar cell having a crystalline structure with crystal planes, the solar cell comprising:
 a germanium substrate;   at least one p-n junction formed atop the germanium substrate, the at least one p-n junction including group III elements and group V elements;   a solar cell window layer formed atop the at least one p-n junction;   a patterned cap layer formed atop the solar cell window layer, the patterned cap layer being electrically connected to the solar cell window layer, the patterned cap layer exposing a light-input portion of the solar cell window layer;   an electrical insulator layer formed atop the solar cell window layer, adjacent the patterned cap layer; and   a metal layer formed on a portion of the electrical insulator layer and on a portion of the patterned cap layer, the metal layer defining a busbar of the solar cell, the busbar bridging the electrical insulator layer and the patterned cap layer, the busbar being disposed above the at least one p-n junction.   
     
     
         8 . A solar cell made of semiconductor materials, the solar cell having a crystalline structure with crystal planes, the solar cell comprising:
 a germanium substrate;   at least one p-n junction formed atop the germanium substrate, the at least one p-n junction including group III elements and group V elements;   a solar cell window layer formed atop the at least one p-n junction;   a patterned cap layer formed atop the solar cell window layer, the patterned cap layer being electrically connected to the solar cell window layer, the patterned cap layer exposing a light-input portion of the solar cell window layer;   an electrical insulator layer formed atop the patterned cap layer; and   a metal layer formed on a portion of the electrical insulator layer and on a portion of the patterned cap layer, the metal layer defining a busbar of the solar cell, the busbar bridging the electrical insulator layer and the patterned cap layer, the busbar being disposed above the at least one p-n junction.